Cryogenic systems for separating scrap plastic particles from various contaminants, including metal, are known and include prior patented systems in which cryogenically treated articles are passed to an impact mill. Separation system patents which are known to applicant are the U.S. patents identified as follows:
______________________________________ 2,879,005 Jarvis 3,885,744 Drage 4,025,990 Lovette, Jr. 4,073,443 Danioni 4,251,034 Corr et al 4,342,647 McMillan et al 4,406,411 Gall et al 4,483,488 Luff et al 4,809,854 Tomaszek ______________________________________
These patents disclose various improvements in the basic system. One of the problems with known processes in which impacting of the frozen flakes has occurred after cryogenic treatment is the difficulty of guaranteeing the virtually complete separation of materials which the present invention achieves because it assures that each flake is individually impacted and is not masked or shielded during impact by another flake or particle. The known systems do not individually impact the flakes in the manner to be described.